1. Field of the Invention
The present invention relates to an air conditioning apparatus for vehicles which air-conditions a vehicle interior compartment and, more particularly, an air conditioning apparatus for an electrically-powered vehicle having no engine coolant as a heating source.
2. Related Art
Conventionally, as engine coolant cannot be used as a heat source for heating in electrically-powered vehicles having no engines, it is proposed as shown in FIG. 10 to use a refrigerant condenser 100 of a refrigeration cycle as a heat-exchanger for heating (heating heat-exchanger). In this system, the refrigerant flow is changed over by a four-way valve 110 in correspondence with operation modes (cooling, heating dehumidifying and the like). In the cooling operation for instance, as shown by the arrow C in FIG. 10, the refrigerant discharged by the refrigerant compressor 120 flows from the four-way valve 110 through a check valve 130, an exterior heat-exchanger 140, electric-type expansion valve 150, a refrigerant evaporator 160 used as a heat-exchanger for cooling (cooling heat exchanger), accumulator 170 and back to the refrigerant compressor 120. Thus, the air blown off from a blower 180 is cooled by a heat exchange with a low temperature refrigerant flowing through the refrigerant evaporator 160 and is blown off into the vehicle compartment through a selected air outlet (e.g., Face-side air outlet 190). The cool air cooled by the refrigerant evaporator 160 is not heated by the refrigerant condenser 100 at this time, because the refrigerant does not flow through the refrigerant condenser 100.
In the heating operation, as shown by the arrow H in FIG. 10, the refrigerant discharged by the refrigerant compressor 120 flows through the four-way valve 110, the refrigerant condenser 100, an electric-type expansion valve 200, a check valve 210, the exterior heat-exchanger 140, an electromagnetic valve 220, accumulator 170 and back to the refrigerant compressor 120. Thus, the air blown off from the blower 180 is heated by a heat exchange with a high temperature refrigerant flowing through the refrigerant condenser 100 and is blown off into the vehicle compartment through a selected blow-off outlet (e.g., Foot-side air outlet 230). The air blown off by the blower 180 is not cooled by the refrigerant evaporator 160 at this time, because the refrigerant does not flow through the refrigerant evaporator 160.
In the dehumidifying operation, as shown by the arrow D in FIG. 10, the refrigerant discharged by the refrigerant compressor 120 flows through the four-way valve 110, the refrigerant condenser 100, the electric-type expansion valve 200 (fully opened not to work as an expansion valve), the check valve 210, the exterior heat-exchanger 140, the electric-type expansion valve 150, the refrigerant evaporator 160, the accumulator 170 and back to the refrigerant compressor 120. Thus, the air blown off from the blower 180 is cooled (dehumidified) by the refrigerant evaporator 160 and then heated again by the refrigerant condenser 100. The air is blown off into the vehicle compartment through a selected blow-off outlet (e.g., defroster air outlet 240).
In the above heat pump cycle in which the refrigerant flow is changed over in correspondence with the operation modes, as the four-way valve 110 which is expensive is used, the entire cost of the air conditioner becomes high.
The inventors of the present application has considered a refrigeration circuit which eliminates the four-way valve 110 as shown in FIG. 11 to reduce product cost. In this refrigeration circuit, however, as the refrigerant under high temperature and high pressure discharged from the refrigerant compressor 120 continuously through the refrigerant condenser 100, the cold air cooled by the refrigerant evaporator 160 is heated again by the refrigerant condenser 100 and blown off from the Face-side outlet 190 as warm air during cooling operation. For overcoming this problem, it is possible to provide a refrigeration circuit in which the refrigerant discharged from the refrigerant compressor 120 flows bypassing the refrigerant condenser 100 during the cooling operation. However, as not only the refrigeration circuit becomes complicated but also the number of parts such as electromagnetic valves, check valves and the like greatly increases, the merit (cost-down) of eliminating the four-way valve 110 is cancelled.